[Libguestfs] Status of R/W UFS

[Richard W.M. Jones]

On Tue, Jan 28, 2014 at 08:16:45PM -0500, Andre Goree wrote:
> Is r/w to a UFS partition using 'guestmount' still an impossibility?
> From everything I've found, it seems to be something that is not
> possible at the moment.  I was just wondering if that has changed or
> if there are plans to change that?

libguestfs just uses the Linux kernel's ufs driver.  If the Linux
kernel gets fixed, we get the ability automatically.

> Here is the issue I'm experiencing:
> 
> ~# guestmount --rw -a ${disk_path}/${disk_name} -m /dev/sda4
> /tmp/freebsd-master
> libguestfs: error: mount_options: /dev/vda4 on /: mount: wrong fs
> type, bad option, bad superblock on /dev/vda4,
>        missing codepage or helper program, or other error
>        In some cases useful info is found in syslog - try
>        dmesg | tail  or so
> guestmount: '/dev/sda4' could not be mounted.  Did you mean one of
> these?
>         /dev/sda4 (ufs)

You can pass mount options, if that helps:

  http://libguestfs.org/guestmount.1.html#options
  guestmount --rw -a ... -m /dev/sda4:/:ufstype=44bsd /tmp/freebsd-master

ufstype must be specified exactly, since the root of the problem is
that UFS does not self-identify and exists in many variants.

However ...

> I have the output from '-- guestmount --rw -a
> ${disk_path}/${disk_name} --trace --verbose -m /dev/sda4
> /tmp/freebsd-master' here:  http://pastebin.com/NT2b2HM9

... the error seems to be:

[    1.979202] ufs was compiled with read-only support, can't be mounted as read-write

Basically you need to recompile your kernel with read-write UFS
support (or persuade whoever compiles your kernel to do the same).

> This appears to be a similar problem to this one, in which I
> gathered that r/w to ufs is not possible:
> https://www.redhat.com/archives/libguestfs/2012-June/msg00077.html
> 
> I get the feeling that this is something I'd need to roll my own
> kernel for, or perhaps just the module?  If anyone could point me in
> the right direction, that'd be awesome.  My apologies for the noise
> if this is the wrong list for this type of question.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
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